We are actively investigating issues impacting players' ability to sign in to Destiny on all platforms. Until resolved, players may experience disconnects or be unable to sign in.

There's also been a couple of tweets updating fans:

It’s come to our attention that players are receiving banjo, marionberry and drum errors. Please stand by for updates as we investigate. — Bungie Help (@BungieHelp) March 2, 2015

Investigation into banjo, marionberry, and drum errors is ongoing. Thank you for your patience while we work to resolve this issue. — Bungie Help (@BungieHelp) March 2, 2015

Players are reporting three main error codes: Marionberry, Drum and Banjo. All of which refer to networking and login issues, specifically "trouble connecting to or maintaining a connection to Destiny matchmaking servers". In all three cases players are pointed towards Bungie's Network Troubleshooting Guide. However, given that Bungie is acknowledging the issue and looking into it, it suggests the issue is confined to its end of operations.

There's also a range of suggested fixes over on thisDestiny Reddit thread.